SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c9ebd594cf69006535c827b293daaedf21af85a7e3bf0cccca1c32794cdbb144' 
  AND token = 'k6AHfo2Gfqh78gd2v6CkguTW24Fl9iqAcGDezGchDBY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}